<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category  Zend
 * @package   Zend_TimeSync
 * @copyright Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd     New BSD License
 * @version   $Id: Ntp.php 16209 2009-06-21 19:20:34Z thomas $
 */

/**
 * Zend_TimeSync_Protocol
 */
require_once 'Zend/TimeSync/Protocol.php';

/**
 * NTP Protocol handling class
 *
 * @category  Zend
 * @package   Zend_TimeSync
 * @copyright Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_TimeSync_Ntp extends Zend_TimeSync_Protocol
{
	/**
	 * NTP port number (123) assigned by the Internet Assigned Numbers Authority
	 *
	 * @var integer
	 */
	protected $_port = 123;

	/**
	 * NTP class constructor, sets the timeserver and port number
	 *
	 * @param string  $timeserver Adress of the timeserver to connect to
	 * @param integer $port       (Optional) Port for this timeserver
	 */
	public function __construct($timeserver, $port = 123)
	{
		$this->_timeserver = 'udp://' . $timeserver;
		if ($port !== null) {
			$this->_port = $port;
		}
	}

	/**
	 * Prepare local timestamp for transmission in our request packet
	 *
	 * NTP timestamps are represented as a 64-bit fixed-point number, in
	 * seconds relative to 0000 UT on 1 January 1900.  The integer part is
	 * in the first 32 bits and the fraction part in the last 32 bits
	 *
	 * @return string
	 */
	protected function _prepare()
	{
		$frac   = microtime();
		$fracba = ($frac & 0xff000000) >> 24;
		$fracbb = ($frac & 0x00ff0000) >> 16;
		$fracbc = ($frac & 0x0000ff00) >> 8;
		$fracbd = ($frac & 0x000000ff);

		$sec   = (time() + 2208988800);
		$secba = ($sec & 0xff000000) >> 24;
		$secbb = ($sec & 0x00ff0000) >> 16;
		$secbc = ($sec & 0x0000ff00) >> 8;
		$secbd = ($sec & 0x000000ff);

		// Flags
		$nul       = chr(0x00);
		$nulbyte   = $nul . $nul . $nul . $nul;
		$ntppacket = chr(0xd9) . $nul . chr(0x0a) . chr(0xfa);

		/*
		 * Root delay
		 *
		 * Indicates the total roundtrip delay to the primary reference
		 * source at the root of the synchronization subnet, in seconds
		 */
		$ntppacket .= $nul . $nul . chr(0x1c) . chr(0x9b);

		/*
		 * Clock Dispersion
		 *
		 * Indicates the maximum error relative to the primary reference source at the
		 * root of the synchronization subnet, in seconds
		 */
		$ntppacket .= $nul . chr(0x08) . chr(0xd7) . chr(0xff);

		/*
		 * ReferenceClockID
		 *
		 * Identifying the particular reference clock
		 */
		$ntppacket .= $nulbyte;

		/*
		 * The local time, in timestamp format, at the peer when its latest NTP message
		 * was sent. Contanis an integer and a fractional part
		 */
		$ntppacket .= chr($secba)  . chr($secbb)  . chr($secbc)  . chr($secbd);
		$ntppacket .= chr($fracba) . chr($fracbb) . chr($fracbc) . chr($fracbd);

		/*
		 * The local time, in timestamp format, at the peer. Contains an integer
		 * and a fractional part.
		 */
		$ntppacket .= $nulbyte;
		$ntppacket .= $nulbyte;

		/*
		 * This is the local time, in timestamp format, when the latest NTP message from
		 * the peer arrived. Contanis an integer and a fractional part.
		 */
		$ntppacket .= $nulbyte;
		$ntppacket .= $nulbyte;

		/*
		 * The local time, in timestamp format, at which the
		 * NTP message departed the sender. Contanis an integer
		 * and a fractional part.
		 */
		$ntppacket .= chr($secba)  . chr($secbb)  . chr($secbc)  . chr($secbd);
		$ntppacket .= chr($fracba) . chr($fracbb) . chr($fracbc) . chr($fracbd);

		return $ntppacket;
	}

	/**
	 * Reads the data returned from the timeserver
	 *
	 * This will return an array with binary data listing:
	 *
	 * @return array
	 * @throws Zend_TimeSync_Exception When timeserver can not be connected
	 */
	protected function _read()
	{
		$flags = ord(fread($this->_socket, 1));
		$info  = stream_get_meta_data($this->_socket);

		if ($info['timed_out'] === true) {
			fclose($this->_socket);
			throw new Zend_TimeSync_Exception('could not connect to ' .
                "'$this->_timeserver' on port '$this->_port', reason: 'server timed out'");
		}

		$result = array(
            'flags'          => $flags,
            'stratum'        => ord(fread($this->_socket, 1)),
            'poll'           => ord(fread($this->_socket, 1)),
            'precision'      => ord(fread($this->_socket, 1)),
            'rootdelay'      => ord(fread($this->_socket, 4)),
            'rootdispersion' => ord(fread($this->_socket, 4)),
            'referenceid'    => ord(fread($this->_socket, 4)),
            'referencestamp' => ord(fread($this->_socket, 4)),
            'referencemicro' => ord(fread($this->_socket, 4)),
            'originatestamp' => ord(fread($this->_socket, 4)),
            'originatemicro' => ord(fread($this->_socket, 4)),
            'receivestamp'   => ord(fread($this->_socket, 4)),
            'receivemicro'   => ord(fread($this->_socket, 4)),
            'transmitstamp'  => ord(fread($this->_socket, 4)),
            'transmitmicro'  => ord(fread($this->_socket, 4)),
            'clientreceived' => 0
		);

		$this->_disconnect();

		return $result;
	}

	/**
	 * Sends the NTP packet to the server
	 *
	 * @param  string $data Data to send to the timeserver
	 * @return void
	 */
	protected function _write($data)
	{
		$this->_connect();

		fwrite($this->_socket, $data);
		stream_set_timeout($this->_socket, Zend_TimeSync::$options['timeout']);
	}

	/**
	 * Extracts the binary data returned from the timeserver
	 *
	 * @param  string|array $binary Data returned from the timeserver
	 * @return integer Difference in seconds
	 */
	protected function _extract($binary)
	{
		/*
		 * Leap Indicator bit 1100 0000
		 *
		 * Code warning of impending leap-second to be inserted at the end of
		 * the last day of the current month.
		 */
		$leap = ($binary['flags'] & 0xc0) >> 6;
		switch($leap) {
			case 0:
				$this->_info['leap'] = '0 - no warning';
				break;

			case 1:
				$this->_info['leap'] = '1 - last minute has 61 seconds';
				break;

			case 2:
				$this->_info['leap'] = '2 - last minute has 59 seconds';
				break;

			default:
				$this->_info['leap'] = '3 - not syncronised';
				break;
		}

		/*
		 * Version Number bit 0011 1000
		 *
		 * This should be 3 (RFC 1305)
		 */
		$this->_info['version'] = ($binary['flags'] & 0x38) >> 3;

		/*
		 * Mode bit 0000 0111
		 *
		 * Except in broadcast mode, an NTP association is formed when two peers
		 * exchange messages and one or both of them create and maintain an
		 * instantiation of the protocol machine, called an association.
		 */
		$mode = ($binary['flags'] & 0x07);
		switch($mode) {
			case 1:
				$this->_info['mode'] = 'symetric active';
				break;

			case 2:
				$this->_info['mode'] = 'symetric passive';
				break;

			case 3:
				$this->_info['mode'] = 'client';
				break;

			case 4:
				$this->_info['mode'] = 'server';
				break;

			case 5:
				$this->_info['mode'] = 'broadcast';
				break;

			default:
				$this->_info['mode'] = 'reserved';
				break;
		}

		$ntpserviceid = 'Unknown Stratum ' . $binary['stratum'] . ' Service';

		/*
		 * Reference Clock Identifier
		 *
		 * Identifies the particular reference clock.
		 */
		$refid = strtoupper($binary['referenceid']);
		switch($binary['stratum']) {
			case 0:
				if (substr($refid, 0, 3) === 'DCN') {
					$ntpserviceid = 'DCN routing protocol';
				} else if (substr($refid, 0, 4) === 'NIST') {
					$ntpserviceid = 'NIST public modem';
				} else if (substr($refid, 0, 3) === 'TSP') {
					$ntpserviceid = 'TSP time protocol';
				} else if (substr($refid, 0, 3) === 'DTS') {
					$ntpserviceid = 'Digital Time Service';
				}
				break;

			case 1:
				if (substr($refid, 0, 4) === 'ATOM') {
					$ntpserviceid = 'Atomic Clock (calibrated)';
				} else if (substr($refid, 0, 3) === 'VLF') {
					$ntpserviceid = 'VLF radio';
				} else if ($refid === 'CALLSIGN') {
					$ntpserviceid = 'Generic radio';
				} else if (substr($refid, 0, 4) === 'LORC') {
					$ntpserviceid = 'LORAN-C radionavigation';
				} else if (substr($refid, 0, 4) === 'GOES') {
					$ntpserviceid = 'GOES UHF environment satellite';
				} else if (substr($refid, 0, 3) === 'GPS') {
					$ntpserviceid = 'GPS UHF satellite positioning';
				}
				break;

			default:
				$ntpserviceid  = ord(substr($binary['referenceid'], 0, 1));
				$ntpserviceid .= '.';
				$ntpserviceid .= ord(substr($binary['referenceid'], 1, 1));
				$ntpserviceid .= '.';
				$ntpserviceid .= ord(substr($binary['referenceid'], 2, 1));
				$ntpserviceid .= '.';
				$ntpserviceid .= ord(substr($binary['referenceid'], 3, 1));
				break;
		}

		$this->_info['ntpid'] = $ntpserviceid;

		/*
		 * Stratum
		 *
		 * Indicates the stratum level of the local clock
		 */
		switch($binary['stratum']) {
			case 0:
				$this->_info['stratum'] = 'undefined';
				break;

			case 1:
				$this->_info['stratum'] = 'primary reference';
				break;

			default:
				$this->_info['stratum'] = 'secondary reference';
				break;
		}

		/*
		 * Indicates the total roundtrip delay to the primary reference source at the
		 * root of the synchronization subnet, in seconds.
		 *
		 * Both positive and negative values, depending on clock precision and skew, are
		 * possible.
		 */
		$this->_info['rootdelay']     = $binary['rootdelay'] >> 15;
		$this->_info['rootdelayfrac'] = ($binary['rootdelay'] << 17) >> 17;

		/*
		 * Indicates the maximum error relative to the primary reference source at the
		 * root of the synchronization subnet, in seconds.
		 *
		 * Only positive values greater than zero are possible.
		 */
		$this->_info['rootdispersion']     = $binary['rootdispersion'] >> 15;
		$this->_info['rootdispersionfrac'] = ($binary['rootdispersion'] << 17) >> 17;

		/*
		 * The local time, in timestamp format, at the peer
		 * when its latest NTP message was sent.
		 */
		$original  = (float) $binary['originatestamp'];
		$original += (float) ($binary['originatemicro'] / 4294967296);

		/*
		 * The local time, in timestamp format, when the latest
		 * NTP message from the peer arrived.
		 */
		$received  = (float) $binary['receivestamp'];
		$received += (float) ($binary['receivemicro'] / 4294967296);

		/*
		 * The local time, in timestamp format, at which the
		 * NTP message departed the sender.
		 */
		$transmit  = (float) $binary['transmitstamp'];
		$transmit += (float) ($binary['transmitmicro'] / 4294967296);

		/*
		 * The roundtrip delay of the peer clock relative to the local clock
		 * over the network path between them, in seconds.
		 *
		 * Note that this variable can take on both positive and negative values,
		 * depending on clock precision and skew-error accumulation.
		 */
		$roundtrip                = ($binary['clientreceived'] - $original);
		$roundtrip               -= ($transmit - $received);
		$this->_info['roundtrip'] = ($roundtrip / 2);

		// The offset of the peer clock relative to the local clock, in seconds.
		$offset                = ($received - $original + $transmit - $binary['clientreceived']);
		$this->_info['offset'] = ($offset / 2);

		$time = (time() - $this->_info['offset']);

		return $time;
	}
}
